Mayflies form an independent order of insects (Ephemeroptera). Thus, they are neither flies nor mosquitoes. There are 2800 mayfly species worldwide, with about 100 species in Central Europe.
Adult mayflies usually live only 1 to 4 days, some even less. During this time, they do not feed, but devote themselves solely to reproduction. In contrast, mayflies live 1 to 3 years as aquatic larvae, with sometimes more than 20 molts.
Mayflies reach a body length of approximately 0.3 to 4 cm, and a wingspan of up to 4 cm. They have short antennae and long legs. The adults fold their wings vertically to the ground above their bodies (like butterflies).
Mayflies emerge as adults from spring to autumn, not necessarily in May. Currently, they are hatching from a water barrel in our garden in great numbers. To photograph them I could convince a few to pause on their journey to reproduction on a white porcelain plate.